All That Matters
by Kicon
Summary: "I need you." In which Dean makes Cas promise to kill him if he loses control of the First Blade and Cas is suffering the repercussions of the stolen Grace. A possible ending to season 9. Ambiguous/implied Destiel.


_All That Matters_

* * *

Dean paced back and forth along the sidewalk outside the motel. He'd lost track of how long he'd been out there after the first half hour. A whole mixture of emotions raged within him. Anticipation, fear, eagerness, disgust...

He growled and tugged at his hair, then straightened up and looked at the sky, full of resolve –

And then turned away again.

"_Fuck_," he swore under his breath, pressing the heels of his hands into his eyes.

There was a rush of feathers and a groan of pain behind him, and Dean turned around quickly, finding a pair of blue eyes staring at him in the darkness.

"Hello, Dean," Cas said gruffly, leaning against the burnt out light pole and tipping his head back as if he couldn't stand on his own.

"You look like shit," Dean replied, then frowned. "Why are you here? I didn't pray to you."

"But you wanted to," Cas answered, staring at him with the same old intensity that never failed to make Dean squirm. "I can feel that, too."

He scrunched his eyebrows together. "So you can feel when people _want_ to pray to you?"

"No, only you."

Dean's face heated up, but he ignored it and switched subjects.

"How can you still fly?" he asked, walking over to Cas. He half raised a hand to touch Cas' forehead, to see if he was feverish or sick, but his hand fell back to his side. "I thought your new wings were broken ones."

"Not broken, no," Cas replied with a shake of his head. "Not on me they're not. But they are highly damaged. I can still fly, but it hurts me very badly. I can't do it very often at all."

"You shouldn't have – "

"_Dean_," Cas interrupted tiredly, and their eyes met. One of their silent conversations passed through them, and Dean wasn't even sure what exactly they'd said, but that was the end of that.

"So, uh, how're things with you?" Dean asked awkwardly. "Haven't seen you in a while. Any updates on the angel factions? On Metatron?"

"War is approaching soon," Cas replied, a look of pain crossing over his face. Although whether that had to do with his brothers and sisters fighting or with his current state of being, Dean didn't know. "As for Metatron, he's still up in the air. Gadreel is still killing for him. I was investigating a new murder when I felt your desperation."

Dean shook his head. "You – "

"It's okay, I want to be here," Cas interrupted, then hitched a breath as he slid a little down the light pole with a grimace.

"You're not gonna when I tell you what's happening in a few hours," Dean told him.

"You're going to try to kill Abaddon," Cas stated matter-of-factly. "You, Sam, and Crowley are going to the fields on the north side of town and end this once and for all."

Dean blinked with surprise. "Well. I guess you _do_ know what's happening in a few hours."

"I told you once, a long time ago," Cas said slowly. "Much of the time, I'd rather be with you. And Sam. This time is no different."

Dean ran a nervous hand through his hair. "Yeah, well...I have a favor to ask."

"I will do my best to fulfil it."

Dean glared at him. "You don't even know what I want you to do," he snapped.

Cas turned his head and his big, luminous eyes met Dean's. "I know it's you asking."

Dean swallowed and looked away. _Dammit_ why was this so hard? Why was it always like this with Cas? He wondered when exactly Cas had gone from "I don't serve man, and I certainly don't serve you" to "I know it's you asking." He felt like he was always asking, requesting, taking, and Cas was always _giving giving giving_ until he had nothing left.

"You're like the goddamn giving tree," Dean muttered.

"What?" Cas asked, tilting his head to the side.

He shook his head. "Nothing. Listen: tomorrow, in order to kill Abaddon, I, uh…I have to have the First Blade."

He said it nervously, remembering Cas' reaction when he'd found out that Dean had been given the Mark of Cain. Cas had looked so furious that Dean had thought he was going to beat him up into a bloody pulp, but after a moment Cas had sighed brokenly and said, "Have you no sense of self-preservation?"

Cas frowned at the mention of the Blade, like he was still pissed about it, but nodded calmly. "I know."

"But the last time I held it, I..." Dean took a breath as the memory washed over him, making him a little shaky, a little dizzy. "I almost didn't let it go. Sam had to make me, and even then I almost didn't do it. It's like it had a...a sort of control over me."

Cas frowned deeper. "Dean, what are you asking of me?"

"I'm asking..." He licked his lips. "After I kill Abaddon, after we win this thing, if I lose control, if I can't let it go...you have to stop me. Kill me, if that's what it takes."

Cas stared at him blankly. His expression didn't change one bit. Dean wasn't sure what sort of reaction he'd expected from Cas – anger, refusal, an attempt to change his mind – but he definitely hadn't expected this...this _lack_ of reaction.

Finally Cas moved, pushing himself off the light pole, his strength seeming to have returned enough for him to stand without aid. He stared down at the pavement.

"She trained me to kill you."

Dean did a double take. "What? Who?"

"Naomi," Cas replied. "I was meant to kill you, that night in the crypt."

Dean ran a hand over his face in remembrance. He could still feel the pain of Cas' blows as if it had happened yesterday. He could smell the dankness of the crypt and could feel his blood dripping in his eyes. He could feel the fear in his chest like a knot, thinking that this was it – Cas was really going to kill him.

"She trained me," Cas continued, still staring at the sidewalk. "She put me in different environments, different situations, each more real and more vivid than the last. I killed you over a thousand times until I could do it without hesitation."

Cas squeezed his eyes shut as if remembering hurt him. Dean's hand itched and he felt the urge to reach out and grab the angel, tell him it was alright, but he didn't.

"But when it came down to the wire, I couldn't do it," Cas finished, looking up with a somberness that could break Dean's heart. "If I couldn't kill you then, what makes you think I can do it now?"

"Because I'm asking you to," Dean said simply.

Cas shook his head and turned away.

"I mean it, Cas. If I lose control, nobody can stop me except you," Dean insisted. "You'll have to kill me. Smite me, shoot me, whatever – so long as I can't hurt anyone."

Cas sighed. "Dean, there's something you have to know."

Dean nodded. "Okay. Let me hear it."

"You have to know how I became an angel again."

He paused, realizing that he never did hear the story. "Yeah, how _did_ you get your mojo back?"

"I stole it."

Dean stared at him. "I'm sorry..._what?_"

"I stole it," Cas repeated. "I was captured by Malachi. They tortured me, asked me for Metatron's location. I couldn't give it to them, but made them think that I knew. I stole the Grace of one of my captors, of one of my brothers, and then I killed him."

Dean's body went cold as he thought about how that must've affected Cas: to kill another of his brothers, to feel that alien Grace inside him.

"The Grace worked well enough at first," Cas said. "It allowed me to do what I needed to do. It has, however, been uncomfortable since the beginning. Like shoving the wrong key into a lock. It can sometimes fit, but doesn't quite turn."

"What are you saying?" Dean asked worriedly.

Cas sighed. "I knew from the moment I'd taken it that I wouldn't be able to hold on to it forever, but I didn't think it would be this soon."

Dean frowned. "Cas?" he asked warily. "Are you okay?"

Cas shook his head. "The Grace has finally started to reject me. It feels very much like when I held on to those souls from Purgatory. If I don't let it go soon, it will burn me from the inside out, like an angel in an unsuitable vessel."

"And...and – " Dean stammered as he was filled with dread.

"And I'll die," Cas replied solemnly. "Most likely for good this time."

Cas really did look worse for the wear. The guy looked like he hadn't slept in weeks – which he probably hadn't, being an angel and all, but he didn't usually suffer repercussions from it. His face was lined with worry, like it was permanently creased. His posture screamed that he was in pain, even now.

"Dammit, Cas," Dean growled. "Let it go already! Why are you still holding on to it?!"

"Because I need to be able to help you tomorrow."

Dean shook his head. "No. No way in Abaddon's bloody hell. You are _not_ fighting tomorrow. Not unless you get rid of that stupid fucking Grace."

"This is my choice, Dean," Cas replied evenly.

"So tell me this," Dean said, walking over to him. "If you use your angel powers tomorrow in the fight, smite some demons or whatever, does that speed up the process of you burning out?"

"I believe it will, yes."

"And you say _I'm_ masochistic," Dean muttered. "Just give up the Grace and if worse comes to worst tomorrow, shoot me in the head like a normal person."

"Dean, I'm not letting go of the Grace until _after_ tomorrow," Cas replied firmly. "Until you and Sam are safe. Only then will I release it."

Dean shook his head and stood right in front of Cas, their eyes locking and not turning away. He saw that familiar determination in those eyes, the kind that didn't back down. He heaved a sigh.

"You're not going to change your mind, are you?" he asked tiredly.

"No."

"Then you need to promise that you'll kill me if I lose it," Dean said. "Smite me right on the spot. Get Sammy to safety, try to make it so he doesn't see, kill me, then get rid of that Grace."

Cas opened his mouth, probably to protest, but Dean pointed his finger in Cas' face.

"And if you die, I swear to your dad that I will _never_ forgive you," Dean said fiercely. "Promise me."

"I will try not to die," Cas replied. "But I cannot promise that I will kill you."

Dean gritted his teeth. "Cas, you have to do this for me. I want it to be you – nobody else."

"I..." Cas sighed resignedly. "I won't let you lose yourself. I can promise that much."

Dean nodded, figuring it was going to be the best he'd get. "I'll take it."

SPNSPNSPN

Dean's body hummed with power and bloodlust.

In his left hand he held Abaddon's head, her meat suit's vibrant red locks clutched tightly in his bruised fingers. She'd died screaming, howling more desperately than the wind that had blown around them. Her body fell, scorched, to the ground and then he'd chopped it into pieces. She'd shuddered and cried and Dean had enjoyed – had _loved_ – every goddamn second of it.

But he wasn't finished yet.

He turned, looking over their battlefield to look for his next target, for Crowley. He looked out over the bloodied landscape with red-tinted vision, seeing bodies stretched out for miles. Most all of them had been shredded to bits, and those were Dean's work. Sure, Crowley's army, Sam, and Cas had helped, but Dean had been an unstoppable whirlwind of death with the First Blade in his hand.

_The First Blade._

He raised his right hand and stared at it like he'd forgotten it was there. Of course, he hadn't forgotten. How could he forget it when it was whispering, always whispering, telling him things only he could hear. Where to strike, how good it will feel, who to kill next.

No, he hadn't forgotten about it.

It felt like an extension of himself, a powerful extension, with the Mark of Cain on his forearm to complete it. The Mark was glowing red and bright, pulsing energy through his body as it had been doing for the past hour or so. His veins had turned blackish, burning burgundy under his skin. It was giving him power like nothing else had ever done before.

And then there was the hunger.

Always the hunger, the desire, the _lust_. Oh, how had he ever thought there was anything sexier than plunging the Blade into someone's stomach and ripping it right up through their ribcage? Than seeing someone try to take their last dying breath and sputter on the blood in their lungs? Than feeling their muscles contracting around the Blade as they tried to expel the Blade from their flesh?

The Blade was far from the prettiest thing he'd ever seen. Hell, it was far from what people thought of when they heard the _word_ "blade." It was made from a goddamn donkey's jaw, for Christ's sake. Less metal and smooth, and more bone and teeth. But _oh_, could it kill, could it slice, could it destroy.

"Where's Crowley?" Dean roared when he couldn't find the smarmy bastard. "_Where is he?!_"

"He disappeared, Dean," Sam said, unexpectedly close.

Dean whirled on him, dropping Abaddon's head and taking a defensive stance in the process. Sam held his hands up as fear flashed in his eyes. A small part of Dean screamed in protest, demanded that Sammy not be hurt, but the Blade was _whispering_ again, telling him to curl his fingers in Sam's hair just like he'd done with Abaddon.

He pushed it down with a struggle and focused on finding Crowley.

"What do you mean, he disappeared?" Dean growled. "You were supposed to be keeping an eye on him!"

"He and the rest of his army left when you were killing Abaddon," said a different voice.

Dean whirled around again, this time facing Castiel. Cas looked a thousand times worse now than he had before the battle. He looked weary and tired, frayed at the edges in more ways than one. His clothes were ripped and he was cut up and bleeding. He wasn't healing, and Dean could see intermittent sparks of bluish white light peeking out through the wounds – the stolen Grace, he realized with a slight jolt.

"I...I need..." Dean panted, his arm shaking violently now. The Blade demanded _more more more_. More blood, more pain, more chaos. And what was more chaotic than killing one's own brother and best friend?

"We can kill Crowley later, Dean," Cas said calmly. "Right now, you need to put down the Blade."

"_NO!_" Dean roared at that preposterous suggestion. Put _down_ the Blade?! Like he'd ever want to! Even if he did, it felt like it had become a part of him, like the handle had fused with his palm. No, there would be no putting down of the Blade. Only putting it into more bodies.

He grinned at the thought, then fixated his eyes on the closest body to him: that of his angelic friend. He approached Cas with the slowness of a predator stalking its prey. Cas held his hands up wearily.

"Dean, you don't need to do this," he said insistently. "We did what we came to do. We stopped Abaddon, we defeated her army. We _won_."

Dean grabbed a fistful of Cas' trench coat and pulled him close, glaring at him. "There is no winning. Only life and death."

"Cas – " Sam started, taking a step toward them.

"No!" Cas shouted as Dean turned his head to look at his little brother. "Sam, I'm fine. I'm fine. You need to go."

Sam nodded and took several steps backwards, but still didn't leave. Dean turned back to Castiel.

"Dean, this isn't you," Cas said, the words achingly familiar to him. "The Blade is controlling you. You need to fight it, Dean. _Fight it._"

Something flashed in Dean's eyes. It was so quick Cas might've imagined it, but his spirits soared nonetheless.

"I know you can fight this, Dean," Cas persisted. "I know you're in there. _This isn't you_."

Dean's hand shook and he released Cas' coat. Cas stumbled back from him and sagged slightly. He'd used his powers more than he'd planned on during the battle, and he was barely holding himself together. The Grace was pushing out on all sides of him. He wrapped his arms around himself, trying to keep it in for just a little while longer.

"Dean, listen to me," Cas pleaded. "Just let it go."

He shook his head. "No, I...I can't! You can't make me!"

"You're right," Cas replied, nodding. "I can't make you. That's why you have to do it yourself. Do it, Dean. Let it go."

Dean growled. He was struggling. His hand clenched impossibly more around the handle of the blade. He approached Cas again and pointed it at Cas' throat. Sam shouted in protest somewhere behind them. Cas held his hands up, his gaze steady on Dean.

"You have to fight it, Dean," Cas begged. "_Fight_, you pigheaded – "

He cried out as Dean hit Cas over the head with the butt of the Blade. He stumbled back and clutched his head as the Grace pulsed painfully within him, but stood back up.

"I know you, Dean. I know you can fight it," Cas continued.

Dean growled and hit Cas again, then again, and again. Cas was kneeling on the ground, his wounds definitely glowing now from the effort of the Grace inside him trying to escape. Cas could feel the edges of his mind going fuzzy.

"Dean, please," Cas said quietly, looking up at him.

Dean hesitated for a moment before he smashed his fist into Cas' face again. He shook with the struggle of keeping the Blade away from Cas, with the struggle of both wanting and not wanting to kill him. It was both his greatest desire and greatest fear.

"Ki...Kill me," Dean gasped out, the words sounding as if they were ripped from him.

Cas shook his head. "I won't. Dean, think of your brother Sam, think of Charlie – "

Dean kicked Cas in the side this time. "I don't care about them!" he shouted. "I don't care about them unless my Blade is _wedged in their spines!_"

"You _do_ care," Cas insisted, grunting as he sat up. His head was killing him, but he kept on. "You care more than anyone, Dean. It's your weakness and your strength."

"No," Dean snarled. "You're wrong!" But he didn't hit Cas again, so Cas persisted even more, pushing past the agony that was wracking his body as he half-lay on the ground at Dean's feet.

"You care about your family," Cas pressed. "And they care about you so, _so_ much."

Dean was shaking violently now, his eyes bloodshot and his jaw locked. He trembled with the effort of resisting, with the effort of not plunging the Blade into the top of Cas' skull like some sort of twisted crown.

"And they need you," Cas whispered painfully as a small ember of Grace leaked out of the cut on his cheek.

Dean's eyes widened and he sucked in a gasp of air.

Cas nodded as tears filled his eyes, both from the pain of the Grace that was burning him up and from the pain of possibly losing Dean.

"Your family needs you, Dean," Cas declared. "They can't do this without you. _I_ can't do this without you!"

The fingers of Dean's right hand started to tremble, and the Blade's whispering quickly turned to shouting and screaming, making his head feeling like was about to explode.

Cas' body was on fire, and he doubled over for a moment from the torture. He looked up at Dean with pleading, hopeful eyes.

"I need you," he confessed quietly, brokenly, and suddenly Dean's mind was filled with the smell of a dank crypt, with memories of blue eyes and FBI badges being held upside down. He remembered late night, unanswered prayers and scouring Purgatory for one of the few people that mattered to him. He remembered a deep voice telling him that good things happen.

His pinky finger began lifting up from off the hilt of the Blade, and the screaming turned to deafening sirens and shrieks. It was too much. He couldn't do it.

"We both do."

Dean looked up at Sam's voice. He'd approached them without Dean noticing, too concerned with his internal struggle. He was kneeling by Cas, who was practically laying on the ground and looked very close to passing out. His pupils had started to glow slightly, as did the veins around his eyes, as more and more embers of Grace were leaking out and disappearing into the air.

"We need you, Dean," Sam said, voice trembling.

A scream built up in the back of Dean's throat as he pried his fingers off the Blade's hilt with as much effort as if he were trying to bend an iron pipe. Memories of long car rides with his brother filled his mind, of standing on a rooftop with his brother and best friend. He thought about hotel room chats and fighting both each other and the enemy. He thought about all of this as he tore his fingers off of the handle.

The scream ripped itself from his vocal cords as he threw the Blade away from him and he felt as if he'd been shredded apart, body and soul. He fell to his knees and tears rolled down his face as the whispering left his mind. He reached out with shaky hands and grabbed Sam and Cas, curling his fingers into their jackets.

"Cas, I did it," he sobbed with abandon. "Now it's your turn. You gotta let it go."

Cas gave him a fleeting smile, then grunted with pain. "I...I'm sorry, Dean, Sam," he whispered. "I think it's...too late."

"N-No," Dean said in a tiny, pitiful voice. "No!"

Cas smiled again, then turned his gaze skyward as he stretched his mouth open wide and his body began to glow white. The bluish white light that Dean had learned to recognize as Grace began to float out. Cas' body shook like he was having a seizure and Dean and Sam could only watch in horror. The Grace left Cas as then burned so bright that the Winchesters had to close their eyes. Then the brightness disappeared and Dean could only assume that the Grace had winked out of existence, its true host being dead.

"Cas?" Dean asked in fear.

Cas' eyes were closed and his body was completely limp. His wounds continued to bleed sluggishly, and Dean cringed, knowing that most of them were from him. Sam was mumbling protests under his breath as he squeezed Cas' shoulders and shifted the former angel into his lap. Dean shook his head in misery.

"Cas!" he said again, shaking Cas slightly. "You bastard – you promised me! You _promised!_" he screamed pounding the ground with his fists.

"Dean," Sam said softly, and Dean looked up to see that his brother was crying too, big fat tears rolling down his face. Sam closed his eyes as he leaned over and buried his face into Cas' chest. Dean put an arm over Sam and his other arm over Cas and they both cried.

"C...Ca..." a muffled voice said.

Dean froze, his eyes flying open.

"Can't...breathe..."

Dean shoved at Sam to get off and they sat up, staring down at Cas. The new human's lungs moved almost imperceptibly and his eyelids fluttered for what felt like several long moments before they opened.

He smiled weakly up at the disbelieving faces of his beloved Winchesters.

"Per...haps," he said feebly, "I sh...should have h-h-healed mys-self firs..t."

Sam and Dean looked at each other and grinned, and then started laughing. Cas joined in faintly, coughing a couple times. It was desperate, hysterical laughter, but they didn't care because Abaddon was dead and they were alive and together, and that was all that mattered.

Dean shook his head as Sam kept laughing and grumbled at Cas, "You stupid son of a bitch."

Cas just grinned.

* * *

So this was just an idea I had about Dean and the First Blade possibly mirroring Castiel and Naomi's control, and I also threw in my idea of the Grace affecting Cas. I really like it, and I really liked writing Dean under the Blade's influence

Tell me what you think! =)

~Ki


End file.
